ΔLightness, ΔChroma and ΔHue difference values


The lightness, chroma and hue difference values are calculated based on the upper color being the reference color and the lower color being the comparison color. The sign of the values is based on the calculations being done in this upper-to-lower direction, and it tells you which way the value is erring.


To help make some sense of the color difference between the two colors, DeltaMunki will colorize the background of the value that has the greatest contribution to the difference. In other words, the dimension with the greatest difference – lightness, chroma or hue – will have its background changed to red.


Reading ΔLightness


A positive ΔLightness value means the lower comparison color is lighter than the upper reference color, while a negative value means the lower comparison color is darker than the upper reference color.


Reading ΔChroma


A positive ΔChroma value means the lower comparison color is more saturated than the upper reference color, while a negative value means the lower comparison color is less saturated (more grayish) than the upper reference color.


Reading ΔHue


The ΔHue value is a bit different and requires some explanation. The hue difference is displayed as a polar distance in degrees (because people are most familiar with a circular color wheel), and it represents the shortest angular distance between the two colors. In a very simplistic sense, the color wheel starts at zero degrees and goes counter-clockwise (the right-hand rule of angles) in the order red-orange-yellow-green-blue-violet and back to red at 360 (or zero) degrees. A positive value means the lower comparison color is in a counter-clockwise direction from the upper reference color, while a negative value means the lower comparison color is in a clockwise direction from the upper reference color. For example, a red upper color and an orange lower color would display a positive hue difference, while a red upper color and a violet lower color would display a negative hue difference.


Note: The difference calculations are done in the more perceptually uniform CIE LCH color space, so the hue values you see in DeltaMunki will not correspond to hue values from non-uniform HSB/HSV/HSL color spaces.


In addition, while the ΔHue value is displayed in degrees, it is calculated internally as a euclidean distance (straight line distance) between two points in 3D color space. As a result, the background color of the field may change in a way that does not directly correspond to the degree value shown in the field. You can think of it like this… Because the hue is a rotational value, you move a further distance in space per degree near the circumference of a circle than you do near the center. So for less saturated colors, there may be a much greater rotation in hue before the field turns red than for more saturated colors.